1. Technical Field
The present invention relates to surgical instruments and, more particularly, to instruments having rotatable motor-driven arthroscopic cutting blades capable of removing fibrous tissue lying between articulate surfaces in and around joints of the body. In addition, the instrument of the present invention can be used to balance meniscal rims and to evacuate excised tissue.
2. Discussion of the Prior Art
A typical prior art arthroscopic surgical instrument is disclosed in U.S. Pat. No. 4,203,444 (Bonnell et al) and U.S. Pat. No. 4,274,414 (Johnson et al). The disclosed instruments are elongated handpieces serving as a housing for a motor which rotatably drives a cutting blade projecting longitudinally from the forward end of the handpiece. The blade is disposed in an apertured sheath or outer tube through which excised tissue material is aspirated via suction applied through the handpiece. Controls for the motor (i.e., on/off, speed control, etc.) are located at a console and connected to the motor via a cable interconnecting the console with the handpiece.
Surgical instruments of the type described must be fabricated of material capable of withstanding autoclave temperatures (i.e., in excess of 270 degrees Fahrenheit) so that the instrument may be sterilized between surgical procedures. It is recognized in the prior art that cutting blades may be designed to be disposable (i.e., the blades are used for a single procedure and then discarded) so as to avoid the requirement of blade sterilization between procedures. However, the handpiece and the components housed therein must be repeatedly sterilized. On the other hand, the control console, which houses electrical circuitry and controls, is not required to be sterilized between uses. As a consequence, a surgeon cannot operate the console controls during a surgical procedure and must rely on an assistant to do so.
It is also recognized in the prior art that certain cutting blades, designed for specific types of surgical procedures, operate optimally within specified ranges of rotational speed. In some commercially-available systems a switch is provided on the control console to permit the operator to select a speed range that is consistent with the cutting blade to be used. A further control at the console permits the operator to select the desired speed within the selected range. A more recent development (made commercially available by Dynoics, Inc., of Andover, Mass. as the "Advanced Arthroscopic Surgical System") automatically sets the speed range appropriate for the selected cutting blade. This is achieved by providing three different cutting blade adapters (i.e., one adapter for each of the possible speed ranges) by which the cutting blade may be operably engaged with the handpiece. The adapters are coded for the desired speed range by means of one or more magnets at specific locations in the adapters. Reed switches in the handpiece are actuated by respective magnets and transmit the speed range control code information to the console to establish the correct speed range. A manual control at the console permits selection of particular speeds within the established range.
As noted above, prior art instruments of the type described have controls at the console which cannot be operated by the surgeon during a procedure without comprising sterilization. It is desirable, therefore, to provide all of the controls on the handpiece. However, there are a number of obstacles which have precluded placing the controls on the handpiece. Specifically, the entire handpiece must be capable of withstanding the temperatures experienced in an autoclave during sterilization. In addition, the controls should not increase the bulk of the handpiece, particularly in its transverse dimension, since increased bulk renders the handpiece unwieldy to manipulate during surgical procedures. Finally, the controls must be located in a convenient manner so as to permit the surgeon to quickly and easily operate each control, preferably with the one hand that holds the handpiece. Prior to the present invention, the prior art has been unable to overcome this combination of obstacles.
In addition, although it is desirable to provide for automatic setting of speed ranges to optimize specific blade operation, the prior art approach has certain disadvantages. In particular, the coded adapter is an additional part of the system which must be capable of withstanding autoclaving temperatures. Consequently, the adapter is relatively heavy and adds significantly to the overall weight of the handpiece. This adversely affects manipulability of the handpiece during surgical procedures. It is desirable, therefore, to provide for automatic speed range selection while eliminating the extra adapter part.